There are many applications for pipe couplings where it is desired to couple two pipes together with a very strong mechanical connection. An important use of such a coupling is that of joining two pipes in a vehicle exhaust system. In such an application, the pipe joint is exposed to a rugged environment including large temperature variations, roadway dirt, vibrations and forces acting on the pipes of the pipe joint. It is known that during vehicle operation forces are developed which have an axial component on the pipes which tends to pull the pipe joint apart. For this reason, the vehicle manufacturer usually establishes a specification of pull-apart strength which must be met by the exhaust pipe joints. Thus, the ability of the pipe joint to withstand axial forces without slippage or pull-apart movement is very important.
In certain applications in vehicle exhaust systems, it is desired to provide a pipe joint with a very high pull-apart strength and a good fluid seal between the pipes. This has been provided by a wide band clamp of the type in which the band is stretched over a butt joint with tight engagement against both pipes. This pipe coupling is disclosed in the Cassel U.S. Pat. No. 3,905,623 granted Sept. 16, 1975. This patent also discloses a lap joint in which the outer pipe serves as a clamping sleeve and receives the end of the other pipe in overlapping relationship. Force applying means are provided on the clamping sleeve to stretch the sleeve into tight engagement with the inner pipe.
A pipe coupling with a lap joint for exhaust systems with high pull-apart strength and good fluid sealing is also disclosed in the Cassel U.S. Pat. No. 4,056,273 granted Nov. 1, 1977. The coupling disclosed in this patent comprises a wide band clamp with a sealing ring disposed around the inner pipe and having an outer diameter about the same as that of the outer pipe. The wide band clamp covers the sealing ring and the end of the outer pipe, spanning the junction therebetween, and is stretched into tight engagement against the sealing ring and the outer pipe.
Another pipe coupling for lap joints with high pull-apart strength and good fluid sealing is disclosed in Cassel U.S. Pat. No. 4,312,526 granted Jan. 26, 1982. The coupling disclosed in this patent comprises an open sleeve which is stretched around the pipes. The open sleeve comprises a roundish sector and a channel-shaped sector comprising a pair of sidewalls extending radially outwardly from the roundish sector. Force applying means are connected with the sidewalls to draw them together so that the roundish sector of the sleeve is stretched over the pipes.
In certain applications in vehicle exhaust systems, it is desired to provide a pipe coupling of the lap type in which a fluid tight seal is provided with a clamping sleeve or band which engages the outer pipe only, i.e. which does not span the outer pipe and inner pipe. In such a pipe lap joint, the fluid seal is achieved by using an outer pipe with a collapsible sealing ring or zone at its free end which is collapsed into sealing engagement with the inner pipe by tightening a clamping band thereon. The pipe lap joint of this type is disclosed in the Wagner et al U.S. Pat. No. 4,113,289 granted Sept. 12, 1978. This type of lap joint is also disclosed in the aforementioned Cassel U.S. Pat. No. 4,056,273 wherein the collapsible sealing structure is separate from but forms an extension of the outer pipe.
There are applications in automotive exhaust systems in which the desired pull-apart strength cannot be achieved by clamping the end of the outer pipe against the inner pipe. In this type of joint, there is need for improvement to increase the pull-apart strength while retaining the sealing capability of the joint.
A general object of this invention is to overcome certain disadvantages of the prior art and to provide a pipe lap joint with improved pull-apart strength.